This commit is an improvement in the previous fill tool changes in order to improve how the extended strokes are managed. * Now, the algorithm checks if the extend cross a standard stroke, not only extend strokes. * Option to enable or disable the stroke cross checking because this can be slow in very complex scenes. * Added `D` key to toggle stroke cross option. * Option to use only collide strokes to be used as fill limit. If the option to use only collide strokes is enabled, the open extensions are in different color. * Status text now shows mode and the actual extend factor. This commits also contains a refactor of the loops to use arrays as much as possible. Reviewed By: mendio, pepeland Differential Revision: https://developer.blender.org/D16052